I Need Engine Experts! 340 Roller Lifter and Pushrod Issue
Hi folks. I am a moderator on FBBO, so I'm not over here as much (although I would love to have cool A body one day). For now, I'm asking about my 73 Road Runner with a 340. I figure there may be more small block knowledge here, so hopefully someone can help me out.
I need some help from the brain trust please! First some specs:
* Small block LA 340, bored .030" over
* Stroker crank, so now displaces 416 CI
* HAD a hydraulic flat tappet cam (more on that below)
* Aluminum Renegade brand heads
* 1.5 ratio roller rockers
* New hydraulic lifter cam specs: cam lobe lift .340", so lift is .510" with 1.5 ratio rockers
The engine has run over 18,000 miles with the hydraulic lifter flat tappet cam. We are now replacing the flat tappet cam with a hydraulic roller cam. The issue I am having is that the roller lifters are significantly taller than a flat tappet lifter. The roller lifter is .770" taller than the flat tappet lifter (as measured from the bottom of the lifter where it contacts the cam to the "cup" in the lifter where the pushrod contacts the lifter).
So the lifters are taller - who cares? Well, the angle between the lifters and pushrod is excessive. In general, there is a non-ideal angle on a LA block, but it is made even worse with the tall lifters. See picture below where I am pointing:
So I set up and measured the actual lift (or more specifically, valve opening) that the cam was making. See mock up below:
In an ideal world, it would measure .510" (and I realize you never have ideal world). Well, it measured .370". Wow - so it is losing .140" lift!!! The picture below shows the valve train geometry and it looks terrible to me.
Are there better (less tall) lifters? Other ways to address this? Lots of people have put roller cams into small blocks, so what am I missing?
Any help from those who have experienced this would be greatly appreciated - thanks!
Hi folks. I am a moderator on FBBO, so I'm not over here as much (although I would love to have cool A body one day). For now, I'm asking about my 73 Road Runner with a 340. I figure there may be more small block knowledge here, so hopefully someone can help me out.
I need some help from the brain trust please! First some specs:
* Small block LA 340, bored .030" over
* Stroker crank, so now displaces 416 CI
* HAD a hydraulic flat tappet cam (more on that below)
* Aluminum Renegade brand heads
* 1.5 ratio roller rockers
* New hydraulic lifter cam specs: cam lobe lift .340", so lift is .510" with 1.5 ratio rockers
The engine has run over 18,000 miles with the hydraulic lifter flat tappet cam. We are now replacing the flat tappet cam with a hydraulic roller cam. The issue I am having is that the roller lifters are significantly taller than a flat tappet lifter. The roller lifter is .770" taller than the flat tappet lifter (as measured from the bottom of the lifter where it contacts the cam to the "cup" in the lifter where the pushrod contacts the lifter).
So the lifters are taller - who cares? Well, the angle between the lifters and pushrod is excessive. In general, there is a non-ideal angle on a LA block, but it is made even worse with the tall lifters. See picture below where I am pointing:
So I set up and measured the actual lift (or more specifically, valve opening) that the cam was making. See mock up below:
In an ideal world, it would measure .510" (and I realize you never have ideal world). Well, it measured .370". Wow - so it is losing .140" lift!!! The picture below shows the valve train geometry and it looks terrible to me.
Are there better (less tall) lifters? Other ways to address this? Lots of people have put roller cams into small blocks, so what am I missing?
Any help from those who have experienced this would be greatly appreciated - thanks!
